Method of producing bus bars for centralized power distribution unit

ABSTRACT

To produce bus bars, a conductive metal plate is stamped out into a plurality of strips simultaneously by press molding. Each strip has a tab having an L-shaped cross-section defined by a curved section and a distal end. The plurality of strips are bent in a thickness direction to obtain a plurality of rings, respectively. The rings are mutually different in diameter and have substantially the same center. The L-shaped tab of each of the rings is disposed such that the distal end of each tab is disposed substantially at a same distance from the center.

CROSS REFERENCE TO RELATED DOCUMENTS

This is a Division of Application Ser. No. 10/281,202 filed Oct. 28,2002, now U.S. Pat. No. 6,894,410, which claims the benefit of JapanesePatent Application No. 2001-330026 filed Oct. 26, 2001. The entiredisclosure of the prior application is hereby incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a centralized power distribution unitwhich is used for performing centralized power distribution on statorwindings of a vehicular thin brushless motor.

2. Description of Related Art

Recently, automobiles with good fuel economy have been in high demand.As one example of automobile manufacturers' efforts to meet thesedemands, hybrid cars with super low fuel consumption have beendeveloped. In particular, a hybrid car has been proposed recently whichis provided with an auxiliary power mechanism (a motor assist mechanism)in which an engine provides the main power and a DC brushless motorassists the engine upon acceleration or the like.

The motor assist mechanism is subject to much constraint ininstallation, since a brushless motor constituting the motor assistmechanism is disposed in a limited space, for example, a space betweenan engine and a transmission in an engine compartment. Thus, such abrushless motor is required to have a thin configuration.

A thin brushless motor to be used in the motor assist mechanism of avehicle includes a rotor directly connected to a crankshaft of theengine, and a ring-like stator enclosing the rotor. The stator includesmany magnetic poles that have windings on cores, a stator holder thatcontains the magnetic poles, and a centralized distribution unit thatconcentratedly distributes currents to the windings.

As shown in FIG. 34A, a conventional centralized power distribution unitused in a three-phase DC brushless motor includes three ring-like busbars 101, 102, and 103. Each of the ring-like bus bars 101, 102, and 103includes a ring-like body 104, a terminal portion 105 projectingoutwardly in a radial direction on an outer periphery of the ring-likebody 104, and a plurality of tabs 106 each projecting inwardly in theradial direction on an inner periphery of the ring-like body 104. Eachterminal portion 105 is electrically connected through an electric wireto a battery while each tab 106 is electrically connected through arespective electric wire to an end of a respective winding. When thethree ring-like bus bars 101, 102, and 103 are energized, currents areconcentratedly distributed to the windings corresponding to a U phase, aV phase, and a W phase. Consequently, the motor is driven.

SUMMARY OF THE INVENTION

When the conventional centralized power distribution unit is to beproduced, press moldings must be conducted on a conductive metal plate107 using different molds to form ring-like bus bars 101, 102, and 103for the three phases as shown in FIG. 34B.

In order to obtain the ring-like bus bars 101, 102, and 103, theconductive metal plate 107 must have a size which is at least as largerthan the outer diameters of the bus bars 101, 102, and 103. Most of theportions of the metal plate other than the portions which are stampedout into the ring-like shape become wasted. Therefore, conventionally,as seen from the above, the conductive metal plate 107 includes a verylarge useless portion and hence is wasteful. This is a cause ofincreased production costs of a centralized power distribution unit.

The invention has been made in view of the above-discussed problem. Itis an object of the invention to provide a centralized powerdistribution unit for a vehicular thin brushless motor which can beproduced at a small amount of waste of a metal material and at a lowcost. It is another object of the invention to provide a method ofproducing bus bars which are preferably used as excellent components ofthe centralized power distribution unit.

In order to attain these objects, in the invention, a centralized powerdistribution unit for a vehicular thin brushless motor includes: aplurality of bus bars each having a terminal portion to be connected toa battery, and tabs to be respectively connected to windings of astator, the bus bars being disposed correspondingly with phases of themotor; and a resin insulating layer that covers the bus bars. Thecentralized power distribution unit can intensively distribute a currentto the windings, and has a ring-like shape. Each of the bus bars isshaped into a substantially annular shape by bending a molded materialwhich is obtained by stamping out a conductive metal plate into astrip-like shape. In a thickness direction, diameters of the bus barsare set to be different from one another depending on the phase, and thebus bars are stacked in a radial direction of the centralized powerdistribution unit, being separated from one another by a predeterminedgap.

According to the invention, therefore, the bus bars can be configured bymaterials which are stamped out into a strip-like shape, so that it isnot required to use a considerably large conductive metal plate and thebus bars can be obtained with a reduced amount of wasted material. Inthe case of a strip-like shape, the bus bars can be obtained in a statewhere the bus bars are densely placed, and hence the amount of wastedmaterial can be reduced. Therefore, the material cost of the bus barscan be reduced, with the result that the centralized power distributionunit can be produced at a low cost.

In the invention, in a method of producing bus bars used in acentralized power distribution unit of the above-mentioned invention,press molding using a mold is conducted to simultaneously stamp out thebus bars respectively corresponding to the phases from a commonconductive metal plate.

According to the invention, therefore, the material loss is remarkablyreduced as compared with that in a conventional method. Therefore, thematerial cost of the bus bars can be reduced, and the cost of the moldcan be lowered. As a result, the centralized power distribution unit canbe produced at a low cost.

Preferably, when a linear bus bar body is stamped out by the pressmolding, the terminal portion and the tabs are integrally formed in astate where the terminal portion and the tabs are coupled to the bus barbody. In this case, a step of welding or the like is not necessary, andhence the production cost can be reduced as compared with the case wherea terminal portion and tabs which are previously produced are laterattached to the bus bar body. Therefore, the use of such bus barsenables the centralized power distribution unit to be produced at a lowcost.

Preferably, the bus bars are stamped out in a state where the bus barbodies are placed in parallel, and in a state where both ends of the busbar bodies are substantially aligned with one another. According to theconfiguration, the material loss in the stamping process is reduced, sothat further cost reduction can be attained.

Preferably, when the bus bars are laid out in parallel in a row on aconductive metal plate in order to be stamped from the conductive metalplate, the terminal portion and the tabs of one(s) of the bus bars whichis (are) positioned at an outermost side(s) are directed to a center ofthe bus bar row. In this case, a conductive metal plate of a smallerwidth can be used as compared with the case where the terminal portionand tabs of the outermost one(s) of the bus bars are directed to theouter side of the bus bar row. Therefore, the material loss in thestamping process is further reduced, so that still further costreduction can be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomeapparent to one skilled in the art to which the present inventionrelates upon consideration of the invention with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic side elevation view of a thin brushless motor;

FIG. 2 is a schematic wiring diagram of the thin brushless motor;

FIG. 3 is a perspective view of a centralized distribution unit;

FIG. 4 is a front elevation view of the centralized distribution unit;

FIG. 5 is a rear elevation view of the centralized distribution unit;

FIG. 6A is a cross sectional view of the centralized distribution unit;

FIG. 6B is an enlarged cross sectional view of a terminal portion of theunit;

FIG. 6C is an enlarged perspective view of the terminal portion shown inFIG. 6B;

FIG. 7 is a plan elevation view of a terminal portion of the centralizeddistribution unit;

FIG. 8 is a perspective view of an insulating holder;

FIG. 9 is a front elevation view of the insulating holder in which busbars are inserted;

FIG. 10 is an enlarged front elevation view of a part of the insulatingholder;

FIG. 11 is a front elevation view of bus bars from which the insulatingholder is omitted;

FIG. 12 is an enlarged front elevation view of a part of the insulatingholder, illustrating a bus bar non-containing section in the holder;

FIG. 13A is a cross sectional view of the insulating holder taken alongline 13 a—13 a in FIG. 9;

FIG. 13B is a cross sectional view of the insulating holder taken alongline 13 b—13 b in FIG. 9;

FIG. 13C is a cross sectional view of the insulating holder taken alongline 13 c—13 c in FIG. 9;

FIG. 14A is a cross sectional view of the centralized distribution unittaken along line 14 a—14 a in FIG. 4;

FIG. 14B is a perspective view of the centralized distribution unitshown in FIG. 14A;

FIG. 15A is a cross sectional view of the centralized distribution unittaken along line 15 a—15 a in FIG. 4;

FIG. 15B is a perspective view of the centralized distribution unitshown in FIG. 15A;

FIG. 16A is a cross sectional view of the centralized distribution unittaken along line 16 a—16 a in FIG. 4;

FIG. 16B is a perspective view of the centralized distribution unitshown in FIG. 16A;

FIG. 17A is a cross sectional view of the centralized distribution unittaken along line 17 a—17 a in FIG. 4;

FIG. 17B is a perspective view of the centralized distribution unitshown in FIG. 17A;

FIG. 18A is a cross sectional view of a first press apparatus,illustrating the apparatus in an open position;

FIG. 18B is a perspective view of a part of a strip-like blank to bepressed by the first press apparatus shown in FIG. 18A;

FIG. 19A is a cross sectional view of the first press apparatus,illustrating the apparatus in a closed position;

FIG. 19B is a perspective view of a strip-like blank that has beenpressed in the first press apparatus shown in FIG. 19A;

FIG. 20A is a cross sectional view of a second press apparatus,illustrating the apparatus in an open position;

FIG. 20B is a perspective view of a strip-like blank that has beenpressed in the second press apparatus shown in FIG. 20A;

FIG. 21A is a plan elevation view of a strip-like blank, illustratingthe blank in a state before a terminal portion of the bus bar is bent;

FIG. 21B is a longitudinal sectional view of the blank taken along line21 b-21 b in FIG. 21B;

FIG. 22 is a rear elevation view of the insulating holder;

FIG. 23A is an enlarged plan elevation view of a bearing recess;

FIG. 23B is an enlarged perspective view of the bearing recess shown inFIG. 23A;

FIG. 24 is a cross sectional view of an insert-molding mold,illustrating the mold in which the insulating holder is set;

FIG. 25 is a cross sectional view of the insert-molding mold similar toFIG. 24, illustrating the mold into which a molten resin material ispoured;

FIG. 26 is a cross sectional view of the insert-molding mold similar toFIG. 25, illustrating the mold in which a holder support pin and anupper mold member support are retracted;

FIG. 27 is a cross sectional view of the insert-molding mold similar toFIG. 26, illustrating the mold in an open position;

FIG. 28 is a plan view of a conductive metallic plate to be punched intothe strip-like blanks, illustrating a process for producing thecentralized distribution unit;

FIG. 29 is a perspective view of the blanks shown in FIG. 28,illustrating the terminal portion of each of bus bars being bent;

FIG. 30 is a perspective view of ring-like blanks that are formed bybending the blanks shown in FIG. 29, illustrating the bus bars beinginserted into the insulating holder;

FIG. 31 is a perspective view of the blanks shown in FIG. 30,illustrating tabs of the bus bars being bent inward;

FIG. 32 is a perspective view of the blanks shown in FIG. 3 1,illustrating a part of the terminal portions being sealed by a sealingmaterial;

FIG. 33 is a view showing another example of a process of stamping outstrip-like molded materials from a conductive metal plate;

FIG. 34A is a perspective view of conventional ring-like bus bars; and

FIG. 34B is a plan view of a conductive metallic plate from which theconventional ring-like bus bars are to be punched out.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIG. 1, a three-phase thin DC brushless motor 11 to be usedin a hybrid automobile is disposed between an engine 12 and atransmission 13. The thin DC brushless motor 11 includes a rotor 14connected, e.g., directly connected, to a crankshaft of the engine 12,and a ring-like stator 15 enclosing the rotor 14. The stator 15 includesa plurality of magnetic poles that have windings 16 on cores, a statorholder 18 that contains the magnetic poles, and an annular centralizeddistribution unit 17 that concentratedly distributes currents to thewindings 16.

FIG. 2 shows a schematic diagram of the stator 15. As shown in FIG. 2,an end of each phase winding 16 is connected to one of bus bars 22 a, 22b, and 22 c formed in the centralized distribution unit 17 while theother end is connected to a ring-like conductive member (not shown).

As shown in FIGS. 3 to 6, a continuous annular insulating holder 21(FIGS. 6A and 6B) made of synthetic resin is embedded in the centralizeddistribution unit 17. The insulating holder 21 may be made of, forexample, PBT (polybutyrene terephthalate), PPS (polyphenylene sulfide),or the like.

In this embodiment, the insulating holder 21 is made of a PPS containinga glass fiber of 40% by weight. The reason why the insulating holder 21is made of such a material is that the material is superior in itselectrical properties (dielectric strength). In particular, in the thinDC brushless motor 11 in the present embodiment, since voltages to beapplied to the respective phase bus bars 22 a, 22 b, and 22 c are high,it is important to maintain the dielectric strength in the respectivebus bars 22 a, 22 b, and 22 c. The dielectric strength in this case isrequired to be above 2000V. In addition, PPS has a high mechanicalstrength as well as a high heat resistance in comparison with a commonresin such as a PP (polypropylene) or the like.

As shown in FIGS. 8, 9, and 10, the insulating holder 21 is provided onone side with holding grooves 23 a, 23 b, and 23 c extending in thecircumferential direction. The holding grooves 23 a, 23 b, and 23 c aredisposed in parallel at a given distance in the radial direction of theinsulating holder 21. The bus bars 22 a, 22 b, and 22 c corresponding tothe respective phases are individually inserted into the respectiveholding grooves 23 a, 23 b, and 23 c, respectively. The respective busbars 22 a, 22 b, and 22 c are stacked on each other in the radialdirection of the centralized distribution unit 17 with the bus barsbeing spaced from each other at a given distance. Accordingly, therespective holding grooves 23 a, 23 b, and 23 c serve to hold therespective bus bars 22 a, 22 b, and 22 c in the precise positions. Theinsulating holder 21 and bus bars 22 a, 22 b, and 22 c are entirelycovered with a resin insulation layer 25. This covering accomplishesindividual insulation between the respective bus bars 22 a, 22 b, and 22c.

The resin insulation layer 25 is made of a PPS containing a glass fiber,similar to the insulating holder 21. The reason why this material isused in the resin insulation layer 25 is that the material is superiorin its electric properties (dielectric strength), heat resistance, andmechanical strength, similar to the reason it is used in the insulatingholder 21. The material in the resin insulation layer 25 utilizes asynthetic resin.

In this embodiment, the bus bar 22 a at the inside layer corresponds toa W phase, the bus bar 22 b at the intermediate layer to a U phase, andthe bus bar 22 c at the outside layer to a V phase, respectively. Forconvenience of explanation, the W phase bus bar 22 a is referred to asthe “inside bus bar 22 a” hereinafter, the U phase bus bar 22 b as the“intermediate bus bar 22 b,” and the V phase bus bar 22 c as the“outside bus bar 22 c,” respectively.

The respective bus bars 22 a, 22 b, and 22 c will be explained below.The respective bus bars 22 a, 22 b, and 22 c are formed beforehand bypunching out a conductive metallic plate made of a copper or a copperalloy into a strip-like blank using a press apparatus, and bending theblank in the thickness direction to form a discontinuous annularconfiguration from which a part of an arc is removed (substantially aC-shape). The diameters of the respective bus bars 22 a, 22 b, and 22 care set to be larger in order from the inside layer to the outsidelayer. The formed respective bus bars 22 a, 22 b, and 22 c are insertedinto the respective holding grooves 23 a, 23 b, and 23 c. This makes iteasy to assemble the respective bus bars 22 a, 22 b, and 22 c in theinsulating holder 21.

As shown in FIGS. 8 to 11, the respective bus bars 22 a, 22 b, and 22 care provided with respective pluralities of projecting tabs 41 a, 41 b,and 41 c to which the respective windings 16 are connected. Therespective tabs 41 a, 41 b, and 42 c are punched out from the conductivemetallic plate simultaneously when the respective bus bars 22 a, 22 b,and 22 c are punched out from the plate by the press apparatus.Consequently, the respective bus bars 22 a, 22 b, and 22 c and therespective tabs 41 a, 41 b, and 41 c are formed integrally together asone piece by a single pressing step. This simplifies the productionprocess in comparison with a process in which the respective tabs 41 a,41 b, and 41 c are coupled to the respective bus bars 22 a, 22 b, and 22c by welding.

Six of each of tabs 41 a, 41 b, and 41 c are provided on the respectivebus bars 22 a, 22 b, and 22 c. The respective tabs 41 a, 41 b, and 41 cin the respective phase are arranged at an even angular distance (i.e.,60 degrees with respect to the center) in the circumferential directionof the respective bus bars 22 a, 22 b, and 22 c. Removed portions 42 ofthe respective bus bars 22 a, 22 b, and 22 c are displaced from eachother by an angle of 20 degrees in the circumferential direction.Consequently, eighteen of the tabs 41 a to 41 c in total are arranged atan even angular distance of 20 degrees with respect to the center in thecircumferential direction of the centralized distribution unit 17. Asshown in FIG. 11, in the present embodiment, in the case where theremoved portion 42 of the outside bus bar 22 c is set to be a reference,the intermediate bus bar 22 b is arranged away from the reference by +20degrees in the clockwise direction. Meanwhile, the inside bus bar 22 ais arranged away from the reference by −20 degrees in thecounterclockwise direction.

The respective tabs 41 a, 41 b, and 41 c of the respective bus bars 22a, and 22 b, and 22 c are bent into L-shapes in cross section to directthe distal ends of them to the center of the centralized distributionunit 17.

Each distal end of the respective tabs 41 a, 41 b, and 41 c projectsinwardly in the radial direction from the inner periphery of thecentralized distribution unit 17. Each winding 16 is connected to arespective projecting portion. The respective tabs 41 a, 41 b, and 41 care different in length. The distal end of each of the respective tabs41 a, 41 b, and 41 c is arranged on the same distance from the center ofthe centralized distribution unit 17. Accordingly, the respective tabs41 a, 41 b, and 41 c of the respective bus bars 22 a, 22 b, and 22 c arelonger in length in the radial direction of the centralized distributionunit in order from the inside bus bar 22 a to the outside bus bar 22 c.

As shown in FIGS. 15A and 15B, the tabs 41 b of the intermediate bus bar22 b are, at the section covered by the resin insulation layer 25,provided with a curved portion 44 raised in the height direction of thewalls 43 a, 43 b, 43 c, and 43 d that define the holding grooves 23 a,23 b, and 23 c. The curved portion 44 goes around the top side of theinside bus bar 22 a (i.e., another bus bar) in the resin insulationlayer 25. The curved portion 44 can provide an increased distancebetween the tabs 41 b and the adjacent bus bar.

As shown in FIGS. 16A and 16B, the tabs 41 c of the outside bus bar 22 care, at the section covered by the resin insulation layer 25 providedwith a curved portion 45 raised in the height direction of the walls 43a to 43 d. The curved portion 45 goes around the top sides of theintermediate bus bar 22 b as well as the inside bus bar 22 a (i.e.,other bus bars) in the resin insulation layer 25. The curved portion 45can provide an increased distance between the tabs 41 c and the adjacentbus bars. Since the curved portion 45 goes around two bus bars 22 a and22 b, the curved portion 45 is longer than the curved portion 44 of thetab 41 b on the intermediate bus bar 22 b.

As shown in FIGS. 14A and 14B, the tabs 41 a of the inside bus bar 22 ahave no curved portion on the proximal end, but rather have aright-angled portion. The tabs 41 a are not required to be at anincreased distance, since there is no adjacent bus bar for the tabs togo around.

As shown in FIGS. 14A and 14B, inside projecting pieces 47 are formedintegrally with wall 43 b, and are positioned between tab formingsections of the inside bus bar 22 a from tab non-forming sections of theintermediate bus bar 22 b adjacent the inside bus bar 22 a. The insideprojecting pieces 47 can provide an increased creepage distance betweenthe inside bus bar 22 a and the intermediate bus bar 22 b adjacent theinside bus bar 22 a. Six inside projecting pieces 47 in total, made of asynthetic resin, are provided on the wall 43 b and arranged at an evenspacing in the circumferential direction of the insulating holder 21.The respective inside projecting pieces 47 correspond in position to therespective tabs 41 a formed on the inside bus bar 22 a. The portions ofwall 43 b having the inside projecting pieces 47 are higher than theportions of wall 43 b that space the tab non-forming sections of theinside bus bar 22 a and intermediate bus bar 22 b.

As shown in FIGS. 15A and 15B, an outside projecting piece 48 is formedintegrally with wall 43 c that spaces a tab forming section of theintermediate bus bar 22 b from a tab non-forming section of the outsidebus bar 22 c adjacent the intermediate bus bar 22 b. The outsideprojecting piece 48 can provide an increased distance between theintermediate bus bar 22 b and the outside bus bar 22 c adjacent theintermediate bus bar 22 b. Six outside projecting pieces 48 in total,made of a synthetic resin, are provided on the wall 43 c and arranged atan even spacing in the circumferential direction of the insulatingholder 21. The respective outside projecting pieces 48 correspond to therespective tabs 41 b formed on the intermediate bus bar 22 b. Theportions of wall 43 c having the outside projecting piece 48 are higherthan the portions of wall 43 c that space the tab non-forming sectionsof the intermediate bus bar 22 b and outside bus bar 22 c.

As shown in FIGS. 3 to 7, the respective bus bars 22 a, 22 b, and 22 care provided on their sides with respective terminal portions 50 w, 50u, and 50 v formed integrally together with the respective bus bars. Therespective terminal portions 50 w, 50 u, and 50 v project outwardly fromthe resin insulation layer 25. The respective terminal portions 50 w, 50u, and 50 v are connected through electric power source cables 51 shownin FIG. 1 to a battery (not shown) for the thin DC brushless motor 11.The respective terminal portions 50 w, 50 u, and 50 v are punched outsimultaneously when the bus bars 22 a, 22 b, and 22 c are punched outfrom the conductive metallic plate by a press apparatus. Accordingly,the respective terminal portions 50 w, 50 u, and 50 v are formedintegrally together as one-piece with the bus bars 22 a, 22 b, and 22 c,respectively, by a single pressing process. This can simplify theproduction process in comparison with a procedure in which therespective terminal portions 50 u, 50 v, and 50 w are welded to therespective bus bars 22 a, 22 b, and 22 c.

As shown in FIGS. 6 and 7, the respective terminal portions 50 u, 50 v,and 50 w are provided on the distal ends with bolt through-holes thatpermit attachment bolts (not shown) for the electric power source cables51 to pass. Resin-containing sections 53 are formed integrally togetherwith the outer periphery of the resin insulation layer 25 to enclose theouter peripheries from the proximal ends to the central portions of therespective terminal portions 50 u, 50 v, and 50 w. The resin-containingsections 53 are filled with sealing material 54 made of an insulativethermosetting resin. The sealing material 54 embeds portions disposednear the proximal ends away from the bolt through-holes 52 and exposedfrom the resin insulation layer 25 on the respective terminal portions50 u, 50 v, and 50 w. Waterproof-ness and airtight-ness functions areenhanced by the sealing material 54 embedding the parts of therespective terminal portions 50 u, 50 v, and 50 w. In the presentembodiment, the sealing material 54 is preferably a silicone-basedthermosetting resin. Alternatively, the thermosetting resin may be anyresin other than a silicone-based resin.

FIG. 28 is a developed view of the bus bars 22 a, 22 b, and 22 c. Asshown in FIG. 28, the respective terminal portions 50 u, 50 v, and 50 ware disposed substantially on longitudinally central parts of therespective bus bars 22 a, 22 b, and 22 c. The numbers of the respectivetabs 41 a, 41 b, and 41 c on opposite sides of the respective terminalportions 50 u, 50 v, and 50 w are preferably the same. In more detail,three tabs 41 a, 41 b, and 41 c are provided on one side of therespective terminal portions 50 u, 50 v, and 50 w while three tabs 41 a,41 b, and 41 c are provided on the other side of the respective terminalportions 50 u, 50 v, and 50 w. The reason why the same numbers of thetabs 41 a,41 b, and 41 c are provided on the opposite sides of theterminal portions 50 u, 50 v, and 50 w is to permit equal amounts ofcurrent to flow in the tabs 41 a, 41 b, and 41 c.

As shown in FIGS. 6 and 8, the respective terminal portions 50 u, 50 v,and 50 w include embedded sections 55 covered by the sealing material 54on their proximal ends, and exposed sections 56 having the boltthrough-holes 52 and not covered by the sealing material 54 on theirdistal ends. The embedded sections 55 are pressed to form central rampportions 55 a. These central ramp portions 55 a can save material incomparison with central right-angled portions, and reduce weights of thebus bars 22 a, 22 b, and 22 c.

Slits 57 a and 57 b are provided on opposite sides of the embeddedportions of the respective terminal portions 50 u, 50 v, and 50 w. Bothslits 57 a and 57 b extend in the longitudinal directions of therespective terminal portions 50 u, 50 v, and 50 w. The two slits 57 aand 57 b reduce a part of the embedded section 55, thereby making awidth of the reduced portion narrower than that of a non-reducedportion. Such structure can make a difference in reducing heatcontraction between the resin insulation layer 25 and the bus bars 22 ato 22 c when the resin insulation layer encloses the insulating holder25 during insert molding. The number and width of the slits 57 a and 57b may be changed without lowering mechanical strengths of the respectiveterminal portions 50 u, 50 v, and 50 w. For example, two slits 57 a and57 b may be provided on the opposite sides of the embedded section 55,respectively.

As shown by cross hatching in FIG. 8, parts of the exposed section 56and embedded section 55 on the respective terminal portions 50 u, 50 v,and 50 w are covered by tinning. In more detail, tinning covers an areafrom the distal end of the exposed section 56 to the central rampportion 55 a of the embedded section 55. This tinning can prevent thebus bars 22 a, 22 b, and 22 c from being subject to corrosion byoxidation.

After the respective terminal portions 50 u, 50 v, and 50 w are bent bya first press apparatus 60 shown in FIGS. 18 and 19, a second pressapparatus 61 shown in FIG. 20 further bends them.

The first press apparatus 60 will be explained below with reference toFIGS. 18 and 19. As shown in FIGS. 18 and 19, the first press apparatus60 bends the respective terminal portions 50 u, 50 v, and 50 w. Thefirst press apparatus 60 includes a stationary lower die member 62 and amovable upper die member 63. When the upper die member 63 moves downtoward the lower die member 62, both dies are closed. Conversely, whenthe upper die member 63 moves up away from the lower die member 62, bothdies are opened.

The lower die member 62 is provided on the upper surface with a lowerforming V-shaped recess 62 a and a lower forming V-shaped protrusion 62b adjacent the recess 62 a. A pilot pin 64 is formed at the top of thelower forming protrusion 62 b. When the pilot pin 64 passes through apilot hole 65 formed in the central ramp portion 55 a of each of theterminal portions 50 u, 50 v, and 50 w, the respective terminal portions50 u, 50 v, and 50 w are positioned.

On the other hand, the upper die member 63 is provided on the lowersurface with an upper forming V-shaped protrusion 63 a and an upperforming V-shaped recess 63 b adjacent the protrusion 63 a. The upperforming protrusion. 63 a is opposed to the lower forming recess 62 awhile the upper forming recess 63 b is opposed to the lower formingprotrusion 62 b. When the upper die member 63 moves down toward thelower die member 62 to the closed position, the upper forming protrusion63 a engages the lower forming recess 62 a. The upper forming recess 63b is provided on the bottom surface with an escape recess 66. When thelower and upper die members 62 and 63 are driven to the closed position,the pilot pin 64 enters the escape recess 66, thereby preventing thepilot pin 64 and upper die member 63 from interfering with each other.

Next, a second press apparatus 61 will be explained below by referringto FIG. 20. As shown in FIG. 20, the second press apparatus 61 bendsboundary sections between the respective terminal portions 50 u, 50 v,and 50 w and the respective bus bars 22 a, 22 b, and 22 c. The secondpress apparatus 61 comprises a stationary lower die member 67 and amovable upper die member 68. When the upper die member 68 moves downtoward the lower die member 67, both dies are closed. Conversely, whenthe upper die member 68 moves up away from the lower die member 67, bothdies are opened.

The lower die member 67 is provided on the upper surface with a lowerforming protrusion 67 a that engages the embedded section 55 on therespective terminal portions 50 u, 50 v, and 50 w. An insertion pin 69is formed near the lower forming protrusion 67 a on the lower die member67 to position the terminal portions 50 u, 50 v, and 50 w. When therespective terminal portions 50 u, 50 v, and 50 w are set on the lowerdie member 67, the insertion pin 69 passes through the respective boltthrough-hole 52. When the insertion pin 69 passes through the boltthrough-hole 52, the respective terminal portions 50 u, 50 v, and 50 ware prevented from being displaced.

The upper die member 68 is provided on the lower surface with an upperforming recess 68 a opposing the lower forming protrusion 67 a. When theupper and lower die members 68 and 67 are driven to the closed position,the upper forming recess 68 a engages the lower forming protrusion 67 a.The thickness of the portion of the upper die member 68 other than theportion at which the upper forming recess 68 a is formed is designed sothat the insertion pin 69 on the lower die member 67 does not interferewith the upper die member 68 when the upper and lower die members aredriven to the closed position.

As shown in FIG. 18 a and FIGS. 21A and 21B, a plurality of notches 59extending in the lateral (width) direction are formed on the areas to bebent on the respective terminal portions 50 u, 50 v, and 50 w by thefirst and second press apparatuses 60 and 61. Each notch 59 is formed ina surface of a strip-like blank 92 punched out from the conductivemetallic plate before forming the respective terminal portions 50 u, 50v, and 50 w. In the present embodiment, one notch is formed in onesurface of the strip-like blank 92 corresponding to the respectiveterminal portions 50 u, 50 v, and 50 w, while three notches are formedin the other surface of the blank 92. The strip-like blank 92 is bentinwardly at the notch 59.

Next, a process for bending the respective terminal portions 50 u, 50 v,and 50 w by using the first and second press apparatuses 60 and 61mentioned above will be explained.

As shown in FIGS. 18A and 18B, when the upper and lower die members 63and 62 of the first press apparatus 60 are driven to the openedposition, the strip-like blanks 92 punched out from the conductivemetallic plate are put on the lower die member 62. The pilot pin 64 onthe lower die member 62 passes through the pilot hole 65 formed in arespective strip-like blank 92 to prevent or reduce displacement of theblank 92.

As shown in FIGS. 19A and 19B, when the upper and lower die members 63and 62 are driven to the closed position, the strip-like blank 92 isclamped between the lower forming recess 62 a and the upper formingprotrusion 63 a and between the lower forming recess 62 b and the upperforming protrusion 63 b. Thus, the respective strip-like blanks 92 arebent at the portions corresponding to the respective terminal portions50 u, 50 v, and 50 w to form the respective terminal portions 50 u, 50v, and 50 w. Thereafter, the upper and lower die members 63 and 62 aredriven to the opened position and the strip-like blank 92, in which therespective terminal portion 50 u, 50 v, or 50 w is formed, is removedfrom the lower die member 62.

As shown in FIGS. 20A and 20B, when the upper and lower die members 68and 67 of the second press apparatus 61 are driven to the openedposition, the respective terminal portion 50 u, 50 v, or 50 w formed bythe first press apparatus 60 engages the lower die member 62. Theinsertion pin 69 passes through the bolt through-hole 52 formed in therespective terminal portions 50 u, 50 v, or 50 w to prevent or reducedisplacement of the blank 92.

When the upper and lower die members 68 and 67 are driven to the closedposition, an end of the strip-like blank 92, namely a portioncorresponding to the respective bus bars 22 a, 22 b, or 22 c, is clampedbetween the lower forming protrusion 67 a and the upper forming recess68 a to bend at a right angle the boundary areas between the respectivebus bar 22 a, 22 b, or 22 c and the respective terminal portion 50 u, 50v, or 50 w. Thereafter, the upper and lower die members 68 and 67 aredriven to the opened position and the strip-like blank 92, in which therespective terminal portion 50 u, 50 v, or 50 w is formed, is removedfrom the lower die member 67.

As shown in FIGS. 24 to 27, the resin insulation layer 25 for coveringthe insulating holder 21 is formed by an insert-molding mold 70. Theinsert-molding mold 70 comprises a stationary lower mold member 71 and amovable upper mold member 72. The upper mold member 72 can move to andfrom the lower mold member 71. When the upper mold member 72 moves downto the lower mold member 71, the mold 70 is placed in a closed position.When the upper mold member 72 moves up from the lower mold member 71,the mold 70 is placed in an open position.

A forming recess 71 a in the lower mold member 71 is opposed to aforming recess 72 a in the upper mold member 72. When the lower andupper mold members 72 and 71 are driven to the closed position, theforming recesses 72 a and 71 a define an annular cavity 73. A moltenresin material 90 is poured through a gate (not shown) into the cavity73 to form the resin insulation layer 25.

The upper mold member 72 is provided with upper mold member supports 80that push an upper surface of the insulating holder 21 to be containedin the cavity 73. The upper mold member supports 80 can move out fromand into an inner top surface of the upper forming recess 72 a. Althoughnot shown in the drawings, a plurality of upper mold member supports 80(eighteen in the present embodiment) are provided in the upper moldmember 72. The upper mold member supports 80 are arranged at an evenspacing on the circumference of the insulating holder 21, except for theportions where the terminal portions 50 u, 50 v, and 50 w are located.When the upper mold member supports 80 are advanced out from the upperforming recess 72 a, a plurality of latch grooves 81 formed in the endsof the supports 80 engage the wall 43 b that spaces the inside bus bar22 a from the intermediate bus bar 22 b, and also engage the wall 43 cthat spaces the intermediate bus bar 22 b from the outside bus bar 22 c.Under this engagement condition, distal end surfaces of the upper moldmember supports 80 come into contact with upper end edges of therespective bus bars 22 a, 22 b, and 22 c. Consequently, the upper moldmember supports 80 push the insulating holder 21 (an upper portion ofthe holder 21 in FIG. 24).

The lower mold member 71 is provided with holder support pins 74 thatsupport the insulating holder 21 to be contained in the cavity 73. Theholder support pins 74 can move out from a bottom surface of the lowerforming recess 71 a into the cavity 73 and move from the cavity 73 intothe bottom surface. Although not shown in the drawings, a plurality ofholder support pins 74 (thirty-six pins in the present embodiment) areprovided in the lower mold member 71. The holder support pins 74 arearranged at an even spacing on the circumference of the insulatingholder 21. Each holder support pin is preferably formed into astick-like configuration having a tapered end. Preferably, the taperedend of each holder support pin 74 has a taper angle of about 30 to 150degrees.

As shown in FIG. 22, and FIGS. 23A and 23B, when the holder support pins74 move out from the bottom surface of the lower forming recess 71 ainto the cavity 73, the distal ends of the pins 74 engage bearingrecesses 75 in the lower surface of the insulating holder 21. Thisengagement can prevent displacement of the insulating holder 21 in theradial direction of the cavity 73 when the insulating holder 21 iscontained in the cavity 73. The insulating holder 21 is fixed at aproper position in the cavity 73 by the holder support pins 74 and uppermold member supports 80. Consequently, the resin insulation layer 25 isformed around the insulating holder 21 at a uniform thickness.

Each bearing recess 75 has a taper that reduces the recess in diametertoward the inner top part. Thus, the holder support pin 74 finallyengages the bearing recess 75 while the pin 74 is being guided along theinner periphery of the bearing recess 75. Accordingly, when theinsulating holder 21 is set in the lower forming recess 71 a in thelower mold member 71, the holder support pin 74 does not fail to engagethe bearing recess 75.

Two arcuate ribs 76 a and 76 b are formed around the holder support pin74 on the bottom surface of the insulating holder 21. The ribs 76 a and76 b make a virtual depth of the bearing recess 75 larger. This reducesthe chance of the holder support pin 74 disengaging from the bearingrecess 75 inadvertently and reduces the chance of the insulating holder21 displacing in the cavity 73.

A plurality of notches 77 a and 77 b (two notches in the presentembodiment) are formed between the ribs 76 a and 76 b. The formation ofthe notches 77 a and 77 b allows the resin for forming the resininsulating layer 25 to easily move toward the bearing recesses 75 viathe notches 77 a and 77 b in the state where the holder support pin 74is extracted from the bearing recess 75 during the process of insertmolding the resin insulation layer 25. In the centralized powerdistribution unit 17 in the final production step, the bearing recesses75 are filled with the resin insulation layer 25. The numbers of theribs 76 a and 76 b and the notches 77 a and 77 b can be arbitrarilychanged. When the ribs 76 a and 76 b are formed as one rib having aC-like shape, for example, the notches 77 a and 77 b can be configuredas one notch.

As shown in FIGS. 22, 23, and in FIGS. 14 to 16, the insulating holder21 is provided, in its bottom surface, with a plurality of communicationholes 78 communicating with the holding grooves 23 a, 23 b, and 23 c.The communication holes 78 facilitate the flow of resin for forming theresin insulation layer 25 into the respective holding grooves 23 a, 23b, and 23 c during insert molding. The plural communication holes 78 areprovided on the periphery of the insulating holder 25. In more detail,the respective communication holes 78 are arranged along the holdinggrooves 23 a, 23 b, and 23 c. In addition, as shown in FIG. 10, therespective communication holes 78 are shifted from each other in thecircumferential direction of the insulating holder 21. This means thatonly one communication hole 78 is disposed on the same line in theradial direction of the insulating holder 21.

As shown in FIGS. 22 and 24, the insulating holder 21 is provided on theinner surface with positioning projections 82 the distal ends of whichcome into contact with the inner surface of the lower forming recess 71a when the insulating holder 21 is set in the lower mold member 71. Theplural positioning projections 82 are arranged at an even spacing in thecircumferential direction of the insulating holder 21. When all of thepositioning projections 82 come into contact with the inner surface ofthe lower forming recess 71 a, displacement of the insulating holder 21in its circumferential direction can be substantially eliminated.

As shown in FIGS. 9, 12, and 13, the respective holding grooves 23 a to23 c in the insulating holder 21 are divided into a bus bar containingsection 83 that accommodates the bus bars 22 a to 22 c and a bus barnon-containing section 84 that does not accommodate the bus bars. Firstreinforcement ribs 85 are provided at a given distance in thecircumferential direction of the insulating holder 21 on the holdinggrooves 23 a, 23 b, and 23 c in the bus bar non-containing section 84.The respective first reinforcement ribs 85 are formed integrallytogether with bottom surfaces and inner side surfaces of the walls 43 ato 43 d. partitioning the respective holding grooves 23 a, 23 b, and 23c.

The communication holes 78 that serve to facilitate to flow the moltenresin material 90 into the respective holding grooves 23 a, 23 b, and 23c are formed in the bottom surface of the respective holding grooves 23a, 23 b, and 23 c in the respective sections 83 and 84. Thus, the moltenresin material 90 easily flows into the respective holding grooves 23 a,23 b, and 23 c.

Three holding grooves 23 a, 23 b, and 23 c are provided in the bus barcontaining section 83 in the insulating holder 21 while two holdinggrooves 23 a and 23 b are provided in the bus bar non-containing section84 in the insulating holder 21. That is, there is no holding groove 23 cat the outermost side in the bus bar non-containing section 84. The busbar non-containing section 84 in the insulating holder 21 is narrowerthan the bus bar containing section 83.

Furthermore, the bus bar non-containing section 84 in the insulatingholder 21 is provided on the outer periphery with a second reinforcementrib 86 extending in the circumferential direction of the insulatingholder 21. The second reinforcement rib 86 is formed into an arcuateshape and a radius of curvature of the rib 86 is set to be the same asthe radius of the insulating holder 21.

Next, a process for insert-molding the centralized distribution unit 17by using the insert-molding mold 70 described above will be explainedbelow.

When the mold 70 is driven to the opened position, the insulating holder21 is put in the lower forming recess 71 a in the lower mold member 71.The holder support pins 74 projecting from the lower forming recess 71 aengage the bearing recesses 75 in the insulating holder 21 at the distalends. Thus, the insulating holder 21 is supported in the lower moldmember 71 with the holder 21 being spaced at a certain distance from thebottom surface of the lower forming recess 71 a. At this time, therespective plural positioning projections 82 on the insulating holder 21come into contact with the inner periphery of the lower forming recess71 a at the distal end surfaces. This substantially preventsdisplacement of the insulating holder 21 in the radial direction.

As shown in FIG. 24, when the upper mold member 72 moves down toward thelower mold member 71 to close the mold 70, the cavity 73 is defined inthe mold 70. When the mold 70 is closed, the distal end surfaces of theupper mold member supports 80 projecting from the upper forming recess72 a come into contact with the upper ends of the bus bars 22 a, 22 b,and 22 c. Further, the latch grooves 81 in the distal end surfaces ofthe upper mold member supports 80 engage the walls 43 b and 43 c thatpartition the respective holding grooves 23 a, 23 b, and 23 c.Consequently, the upper mold member supports 80 push the insulatingholder 21 and the bus bars 22 a, 22 b, and 22 c. As described above, theinsulating holder 21 is constrained from upward and downward movement bythe plural holder support pins 74 and plural upper mold member supports80.

As shown in FIG. 25, molten resin material 90 for forming the resininsulation layer 25 is poured through a gate (not shown) formed in oneof the mold members, e.g., the lower mold member 71, into the cavity 73.At this time, the molten resin material 90 that is poured to cover theinsulating holder 21 flows through openings of the respective holdinggrooves 23 a, 23 b, and 23 c into their interiors. In addition, themolten resin material 90 flows through the communication holes 78 in theinsulating holder 21 into the holding grooves 23 a, 23 b, and 23 c. Evenif the molten resin material 90 is applied under pressure to the holdinggrooves 23 a, 23 b, and 23 c in the bus bar non-containing section 84(see FIG. 12) in the insulating holder 21, the first and secondreinforcement ribs 85 and 86 prevent or reduce deformation of the walls43 a to 43 d.

When the molten resin material 90 substantially fills the cavity 73, asshown in FIG. 26, the holder support pins 74 retract into the lower moldmember 71 and the upper mold member supports 80 retract into the uppermold member 72. Although the insulating holder 21 is fully floated inthe cavity 73 without any supports, the insulating holder 21 will notincline in the cavity 73 since the molten resin material 90 is beingpoured into the cavity 73. In addition, the molten resin material 90will fill the holes caused by the retraction of the holder support pins74 and upper mold member supports 80. Furthermore, the molten resinmaterial 90 flows into the bearing recesses 75 in which the holdersupport pins have engaged, the spaces around the bearing recesses 75,and the spaces between and around the upper ends of the walls 43 b and43 c. Thus, the molten resin material 90 covers the insulating holder21.

As shown in FIG. 27, after a given period of time has passed and themolten resin material 90 has cooled and solidified, the insulation layer25 is formed. Thereafter, the upper mold member 72 and the lower moldmember 71 are separated and placed in the opened position, and thecentralized distribution unit 17, in which the insulating holder 21 andthe resin insulation layer 25 are integrated together, is removed fromthe mold 70.

An exemplary process for producing the centralized distribution unit 17is explained below.

(Step of punching a conductive metallic plate)

As shown in FIG. 28, in order to form the bus bars 22 a, 22 b, and 22 cfor a three-phase motor, three strip-like blanks 92 are formed from onerectangular conductive metal plate 91. In this case,the tabs 41 a, 41 b,and 41c, and the terminal portions 50 u, 50 v, and 50 w are stamped outin a state where they are coupled to the respective strip-like blanks92, by a press machine which is not shown.

As shown in FIG. 28, the strip-like blanks 92 which are stamped out fromthe conductive metal plate 91 are laid out along the longitudinaldirection of the conductive metal plate 91 so that they are parallel toone another. The two strip-like blanks 92 which are positioned in theoutermost side are placed so that the tabs 41 a and 41 c and theterminal portions 50 v and 50 w are directed to the center of the busbar row. According to the configuration, the three strip-like blanks 92can be densely laid out (laid out without forming large gaps) in the oneconductive metal plate 91. As a result, the unused areas formed amongthe strip-like blanks 92 are narrowed. Therefore, the amount of wastedmaterial is reduced, and the width of the conductive metal plate 91which is required for obtaining the strip-like blanks 92 can beshortened.

The three strip-like blanks 92 are formed so as to have an approximatelysame length. In the one conductive metal plate 91, the strip-like blanks92 are laid out so that their both ends are substantially aligned withone another. According to the configuration, in the one conductive metalplate 91, the unused areas formed in the vicinities of the both ends ofthe three strip-like blanks 92 are narrowed. As a result, the amount ofwasted material is reduced, and the length of the conductive metal plate91 which is required for obtaining the strip-like blanks 92 can beshortened. Among the tabs protruding from each of the strip-like blanks92, the two tabs which are positioned at endmost portions are formedintegrally with the end portions of the strip-like blanks 92,respectively. Therefore, the lengths of the strip-like blanks 92 can beshortened as compared with the case where, for example, a bus barstructure of a complete annular shape is employed. This also contributesto the reduced length of the conductive metal plate 91 which is requiredfor obtaining the strip-like blanks 92.

In this way, the strip-like blanks 92 are produced from the conductivemetal plate 91 before the bending process are applied to the bus bars 22a to 22 c. Since the strip-like blanks 92 for forming the bus bars 22 a,22 b, and 22 c have a substantially linear shape as shown in FIG. 29,they can be stamped out in parallel. This remarkably contributes to areduced material cost, and to an improved yield as compared with thecase where the strip-like blanks 92 are annularly stamped out.

(First Bending of the Bus Bars)

As shown in FIG. 29, the first and second press apparatuses 60 and 61mentioned above bend the portions corresponding to the terminal portions50 u, 50 v, and 50 win the strip-like blanks 92.

(Second Bending of the Bus Bars)

As shown in FIG. 29, the portions corresponding to the bus bars 22 a, 22b, and 22 c in the strip-like blanks 92 in which the terminal portions50 u, 50 v, and 50 w have been formed are bent in the thicknessdirection to form annular shapes. This bending work is carried out by abending device (not shown). Thus, the bus bars 22 a, 22 b, and 22 c areformed into substantially annular shapes beforehand, before attachingthe bus bars 22 a, 22 b, and 22c to the insulating holder 21.

(Step of Inserting the Bus Bars)

As shown in FIG. 30, the respective bus bars 22 a, 22 b, and 22 c areinserted into the insulating holder 21 that has already been produced.At this time, the bus bars are inserted into the insulating holder 21 inorder from the outermost position to the innermost position. That is,the outside bus bar 22 a, intermediate bus bar 22 b, and inside bus bar22 c are inserted into the insulating holder 21 in that order. If theinside bus bar 22 c is inserted into the insulating holder 21 beforeinserting the intermediate bus bar 22 b, the prior bus bar interfereswith entrance of the latter bus bar.

(Third Bending of the Bus Bars)

As shown in FIG. 31, the respective tabs 41 a, 41 b, and 41 c are bentso that their distal ends are directed to the center of the insulatingholder 21 with the respective bus bars 22 a to 22 c being attached tothe insulating holder 21. The curved portions 44 and 45 are formed onthe proximal ends of tabs of the the intermediate bus bar 22 b andoutside bus bar 22 c, respectively.

(Insert Molding)

As shown in FIG. 32, the resin insulation layer 25 is formed on theouter periphery of the insulating holder 21 to which the bus bars 22 a,22 b, and 22 c have been already attached. This forming process may becarried out by using the insert-molding mold 70 mentioned above.Thereafter, the centralized distribution unit 17 is taken out from theinsert-molding mold 70. Finally, the sealing material 54 fills the resincontaining sections 53 (FIG. 5) formed in the resin insulation layer 25.

Accordingly, effects including the following effects may be obtainedaccording to the above-described embodiment.

(1) The bus bars 22 a, 22 b, and 22 c are formed by stamping out into astrip-like shape from the one conductive metal plate 91. In this case,the bus bars 22 a, 22 b, and 22 c are stamped out from the conductivemetal plate 91, in the state where the bus bars are densely laid out.Therefore, the required area of the conductive metal plate 91 can bemade smaller than that in the case where the bus bars 22 a, 22 b, and 22c are stamped out into a ring-like shape. Consequently, the materialloss is reduced as compared with that in a conventional method, so thatthe material cost of the bus bars 22 a, 22 b, and 22 c can be lowered.As a result, the centralized power distribution unit 17 can beeconomically produced.

(2) The bus bars 22 a, 22 b, and 22 c are simultaneously stamped outfrom the common conductive metal plate 91 by using a mold. In this case,the used area of the conductive metal plate 91 can be reduced to about ahalf of that in the case where the bus bars 22 a, 22 b, and 22 c arestamped out into a ring-like shape, and the material loss is reliablysuppressed. Therefore, the material cost of the bus bars 22 a, 22 b, and22 c can be reduced. Unlike the conventional art, it is not required touse different molds for respective rings. Therefore, the mold cost canbe reduced. As a result, the centralized power distribution unit 17 canbe more economically produced.

(3) The tabs 41 a, 41 b, and 41 c, and the terminal portions 50 w, 50 w,and 50 v are integrally formed, coupled with the bodies of the bus bars22 a, 22 b, and 22 c, respectively. In this case, it is not necessary toattach the tabs 41 a, 41 b, and 41 c, and the terminal portions 50 w, 50w, and 50 v in a subsequent step by welding or the like. Therefore, thenumber of steps of producing the bus bars 22 a, 22 b, and 22 c can bereduced. As a result, the centralized power distribution unit 17 can bemore economically produced.

(4) The bus bars 22 a, 22 b, and 22 c are stamped out from theconductive metal plate 91 in the state where both ends of the bus barsare substantially aligned with one another, and in the state where thebus bars are placed in parallel. In the conductive metal plate 91,therefore, material loss in the areas of the ends in the longitudinaldirection and the sides in the width direction of the bus bars 22 a, 22b, and 22 c is reduced. Consequently, the material cost of the bus bars22 a, 22 b, and 22 c can be further lowered, so that the centralizedpower distribution unit 17 can be still more economically produced.

(5) Among the bus bars 22 a, 22 b, and 22 c, the bus bars 22 a and 22 cwhich are positioned in the outermost side are laid out in parallel sothat the terminal portions 50 w and 50 v and the tabs 41 a and 41 c aredirected to the center of the bus bar row. According to thisconfiguration, in the conductive metal plate 91, the material loss inthe areas of the ends in the longitudinal direction of the bus bars 22a, 22 b, and 22 c is reduced. Consequently, the material cost of the busbars 22 a, 22 b, and 22 c can be further lowered. As a result, thecentralized power distribution unit 17 can be still more economicallyproduced.

The above-described embodiment of the invention may be modified in, forexample, the following ways.

In the above-described embodiment, the terminal portions 50 w, 50 u, and50 v, and the tabs 41 a, 41 b, and 41 c are formed integrally with thebodies of the bus bars 22 a, 22 b, and 22 c, respectively.Alternatively, the terminal portions 50 w, 50 u, and 50 v, and/or thetabs 41 a, 41 b, and 41 c may be formed by stamping as members separatedfrom the bodies of the bus bars 22 a, 22 b, and 22 c. For example, asshown in FIG. 33, the bus bars 22 a, 22 b, and 22 c are laid out inparallel. The terminal portions 50 u, 50 v, and 50 w are laid out inparallel with the bodies of the bus bars 22 a, 22 b, and 22 c, betweenthe tabs 41 a, 41 b, and 41 c disposed on the bodies of the bus bars 22a, 22 b, and 22 c. According to the configuration, the bus bars 22 a, 22b, and 22 c can be placed more densely, and hence the amount of wastedmaterial in the width direction of the conductive metal plate 91 isfurther reduced. Therefore, the area of the conductive metal plate 91which is required for stamping out the bus bars 22 a, 22 b, and 22 c canbe made smaller than that in the above-described embodiment. In thiscase, the terminal portions 50 w, 50 u, and 50 v, and the tabs 41 a, 41b, and 41 c are later attached to the bodies of the bus bars 22 a, 22 b,and 22 c. As a method of conducting the later attachment, specifically,welding, brazing, soldering, screw fixation, or the like may be used.

In the above-described embodiment, the terminal portion 50 w, 50 u, or50 v, and the tabs 41 a, 41 b, or 41 c are formed on the same side edgeof the corresponding one of the bus bars 22 a, 22 b, and 22 c.Alternatively, the terminal portion 50 w, 50 u, or 50 v, and the tabs 41a, 41 b, or 41 c may be formed on different side edges.

In the above-described embodiment, the invention is applied to thecentralized power distribution unit 17 for the three-phase thin DCbrushless motor 11. The invention is not limited to this, and may beapplied to a centralized power distribution unit for a motor in whichthe phase number is larger than three (or smaller than three). Inaccordance with the phase number, the numbers of the bus bars and theholding grooves may be increased or decreased.

In this case, for example, four bus bars for a four-phase motor may bestamped out from a common conductive metal plate 91, or five bus barsfor a five-phase motor may be stamped out from a common conductive metalplate 91.

In addition to the technical concepts explicitly described above,several technical concepts can be grasped from the embodiment describedabove. The technical concepts will be described together with theireffects.

(1) In a method of producing bus bars used in a centralized powerdistribution unit, the terminal portion and the tabs are formed on asame side edge of the bus bar body. According to the configuration, thestamping can be performed so that the terminal portion and the tabs ofone(s) of the bus bars which are positioned in the outermost side amongthe bus bars which are placed in parallel are directed to the center ofthe bus bar row. Therefore, the material loss in the process of stampingout the bus bars from the conductive metal plate can be reduced, so thatthe centralized power distribution unit for a vehicular thin brushlessmotor can be produced at a low cost.

As described above in detail, according to the invention, it is possibleto provide a centralized power distribution unit for a vehicular thinbrushless motor which can be produced in a relatively simple manner, andwhich has high reliability.

According to the invention, the material cost of the bus bars, and themold cost can be reduced, and hence the centralized power distributionunit for a vehicular thin brushless motor can be produced at a low cost.

According to the invention, the number of steps of producing the busbars can be reduced, and hence the centralized power distribution unitfor a vehicular thin brushless motor can be produced at a low cost.

According to the invention, the loss of the metal material for producingthe bus bars can be further reduced, and hence the centralized powerdistribution unit for a vehicular thin brushless motor can be producedat a lower cost.

While the invention has been described in conjunction with the specificembodiments described above, many equivalent alterative, modificationsand variations may become apparent to those skilled in the art whengiven this disclosure. Accordingly, the exemplary embodiments of theinvention as set forth above are considered to be illustrative and notlimiting. Various changes to the described embodiments may be madewithout departing from the spirit and scope of the invention.

The entire disclosure of Japanese Patent Application No. 2001-330026filed on Oct. 26, 2001 including the specification, claims, drawings andsummary is incorporated herein by reference in its entirety.

1. A method of producing bus bars, comprising stamping out a conductivemetal plate into a plurality of strips, the strips stamped outsimultaneously by press molding, each strip having a tab, the tab havingan L-shaped cross-section defined by a curved section and a distal end;and bending the plurality of strips in a thickness direction to obtain aplurality of rings, respectively, the rings being mutually different indiameter and having substantially a same center, the L-shaped tab ofeach of the rings being disposed such that the distal end of each tab isdisposed substantially at a same distance from the center.
 2. The methodof producing bus bars according to claim 1, wherein, in the step ofstamping out, at least one of (a) a terminal portion and (b) one or moretabs are integrally stamped with a main body of the bus bar.
 3. Themethod of producing bus bars according to claim 2, wherein, in the stepof stamping out, the bus bars are stamped out in a state where the mainbodies are laid out in parallel, and in a state where both ends of themain bodies are substantially aligned with one another.
 4. The method ofproducing bus bars according to claim 1, wherein, in the step ofstamping out, a terminal portion and one or more tabs are integrallystamped with a main body of the bus bar.
 5. The method of producing busbars according to claim 4, wherein, in the step of stamping out, theterminal portion and the one or more tabs of a predetermined one of thebus bars are laid out to be directed to a center of a row of the busbars, the predetermined one of the bus bars being positioned at anoutermost side among the bus bars which are placed in parallel.